Work holder



S. J. KAMINGA July 9, 1968 WORK HOLDER 5 Sheets-Sheet 1 Filed Jan. 3,1966 INVENTOR. 5711/4 J. AflM/A/GA ATTORNEYS S. J. KAMINGA WORK HOLDER 5Sheets-Sheet 2 ATTORNEYS July 9, 1968 Filed Jan. 3, 1966 y 1963 5. J.KAMINGA 3,391,606

WORK HOLDER Filed Jan. 3, 1966 s sheets-sheet 5 Li W 2.,

ma Z m/ NVENTOR.

ATTORNEYS July 9, 1968 5. J. KAMINGA 3,

WORK HOLDER Filed Jan. 3, 1966 5 Sheets-Sheet 4 mvnm'on. 76 sum 1 MM/d/MATTORNEYS s. J. KAMINGA 3,391,606

WORK HOLDER July 9, 1968 Filed Jan. 3, 1966 5 Sheets-Sheet 5 ATTORNEYSUnited States Patent 3,391,606 WORK HOLDER Sylvan J. Kaminga, 2445Fletcher Drive,

Grand Rapids, Mich. 4950.6. Filed Jan. 3, 1966, Ser. No. 518,118 14Claims. (Cl. 90-215) ABSTRACT OF THE DISCLOSURE This disclosure isdirected to a work holder for machine tools, the work holder having workpiece clamping jaws mounted for reciprocating movement past the machinetools. The jaws, on approaching work piece receiving position, openingwhile in movement to receive the work piece upon initiation of returnmovement to work piece clamping of the work piece. The jaws release thework piece upon initiation of return movement to work piece receivingpositioin. The jaws incorporate work piece positioning devices which areautomatically retracted as the jaws leave work piece receiving position.

This invention relates to work piece holders for machine tools forsupporting the work piece as it is moved past the tool which efiects themachining on the work piece. More particularly, this invention relatesto a device intended to automatically reciprocate as a continuous cycleforward and back, past the tool and to receive and release the workpieces automatically with minimum hesitation in its movement. Itpractically eliminates the swell periods characteristic ofconventionalequipment required for either receiving or releasing the work piece. Itis also designed to automatically regulate and vary the speed ofmovement of the work piece beneath the tool, to cause its movement to bemore rapid during those portions of its travel during which the workpiece and tool are not in contact. It is also designed to provide rapidand complete adjustment to adapt the tool from work pieces of oneparticular design to work pieces of another design.

This invention is an improvementover known tools of this type in that itcontinuously reciprocates back and forth between a work piece receivingposition and a work piece releasing position without interruption of itsmotion except for the momentary hesitation when it reverses direction ofmovement after the machine operation and the momentary dwell necessaryto drop a new work piece into place and clamp it.

It automatically releases the completed work piece during the actualreturn stroke of the work holder. Thus, the considerable time delaynormally characteristic of these machines due to hesitation to bothreceive and then release the work piece, is eliminated. When machinetools are used for fabricating large quantities of similar parts on acontinuous production basis, the total amount of time lost due to thenecessity for the machine remaining stationary to receive and todischarge the work piece, adds up, over a period of time, to asubstantial production cost factor. This invention eliminates this timeloss.

The machine is so designed that itcan be quickly and readily adapted tothe machining necessities of various types of machine tools and workpieces of varying designs. Further, the total stroke or distance oftravel of the work piece holder can be limited to only that which isnecessary to complete the machining together with the receiving andrelease of the work pieces. Thus, there is no time lag or waste due tothe machine having to traverse unused portions of its total travelcapability merely because the machine was designed to handle a workpiece significantly bigger or different from than that actually beingmachined.

The machine provides automatic work piece locating moves the work piecepast the machine tool thus eliminating interference with the rapid andautomatic discharge of interference with the rapid and automaticdischarge of the machined work piece when it is to be released.

These and other objects and purposes of this invention will beunderstood by those acquainted with the design and manufacture ofmachine tools upon reading the following specification and theaccompanying drawrngs.

In the drawings:

-FIG. 1 is a plan view of this invention;

FIG. 2 is a partially broken side elevation view of this invention;

FIG. 3 is an end view of the invention taken at the right hand end ofFIG. 2;

FIG. 4 is an enlarged, broken elevation view of the magazine feeder forsupplying the work pieces to this machine;

FIG. 5 is a schematic plan view of the machine with the collet openready to receive a new work piece;

FIG. 6 is a schematic side elevation view showing the work piece beingfed into the open collet;

FIG. 7 is a schematic plan view of the machine with the collet closed atthe moment when the feed actuator initiates its retraction stroke;

FIG. 8 is a schematic side elevation view of the invention as shown inFIG. 7;

FIG. 9 is a schematic plan view of the machine partially through itsretraction stroke;

FIG. 10 is a schematic side elevation view of the invention as it isillustrated in FIG. 9;

FIG. 11 is a schematic plan view of the invention at the limit of itsretraction stroke;

FIG. 12 is a schematic side elevation view of the invention as it isshown in FIG. 11;

FIG. 13 is a schematic side elevation view of the invention immediatelyafter it has initiated its forward or return stroke;

FIG. 14 is a schematic plan view showing the collet returned to workpiece receiving position;

FIG. 15 is an enlarged, fragmentary sectional view of the clamping jawand operating ram, taken along the plane XV'IIXVII of FIG. 6;

FIG. 16 is a fragmentary central sectional view of the travel velocitycontrol unit for the collet; and

FIG. 17 is a schematic diagram of the controls for the invention.

In executing this invention, there is provided a base frame on each endof which are mounted a pair of posts. Extending between the posts arewaybars. The collet assembly is slidably mounted on these ways fortravel from a work piece receiving position to a work piece releasingposition between which the work piece is carried past a tool formachining it. The collet consists of a pair of jaws between which thework piece is clamped. One of the jaws is secured to a reciprocatingpiston which effects movement of the collet assembly back and forthalong its ways. The other jaw is slidably mounted for movement towardand away from the first jaw whereby the collet may be opened to receivethe work piece and closed to clamp it. The second jaw is opened andclosed by a cylinder. This cylinder is mounted to travel with the colletduring its work stroke.

Work stop and positioning fingers are mounted in the collet. These areautomatically positioned to receive and position the work piece when itis received. The collet is then closed to lock the work piece or piecesin position. The initial position of the retraction or work stroke ofthe collet releases the stop fingers permitting them to retreatautomatically from beneath the work piece.

The clamping of the work piece initiates movement of the collet assemblythrough its workv stroke. The movement of the collet is rapid until thework piece. approaches the cutter of the machine tool. At this point, avelocity control mechanism takes over to reduce the speed of travel ofthe collet to that which is suitable for the particular cutting tool andthe type of material being cut. As soon as the piece has passed thecutting tool, the collet trips another sensor, automatically reversingthe direction of travel of the collet. Immediately after reversal, athird sensor is tripped causing the second jaw of the collet to shift torelease position releasing the machined work piece to drop free. Thevelocity control device is inoperative during the return stroke,permitting the machine to return to work piece receiving position at arapid pace where it arrives with the jaws open ready to receive anotherwork piece. During its hesitation in reversing direction to re-enter itswork stroke, the machine automatically causes the release of a new workpiece which drops into the collet, the collet is clamped, and the cyclerepeated.

Referring specifically. to the drawings and to FIGS. 1 and 2, thenumeral indicates a base having a pair of posts 11 adjacent each end.Extending between the posts are a pair of waybars 12 on and betweenwhich is mounted a collet assembly 13. The waybars 12 are fixed and thecollet assembly 13 is mounted to slide along them.

The collet 13 has a first or backing jaw 20, the sides of which haveopenings therethrough for receiving the waybars 12 providing bothsupport and guidance for the jaw during reciprocation. The backing jawhas a clamping plate 21 mounted on one face. The clamping plate 21 has apair of vertical reliefs 22 to partially receive the hereinafterdescribed work piece stops 51.. The clamping jaw 20 .is connected to oneend of a piston 23 which is part of the actuating cylinder assembly 24.The cylinder 24, together with the piston 23, constitute the feedactuator for the invention. The cylinder 24 is stationary and issupported on the terminal plate 25 extending between a pair of the posts11.

The collet 13 has a second or clamping jaw 30, also extending betweenand mounted slidably upon the waybars 12. The clamping jaw has aclamping plate 31 which cooperates with the clamping plate 21 on thebacking jaw 20.

A second pair of waybars 32 extends slidably through the clamping jaw 30and are fixedly secured to the backing jaw 20. These are of sufficientlyheavy construction to prevent bending resulting from the pressuresexerted by the closed clamping jaws 2t) and 30. The clamping jaw 30 isequipped with bearings surrounding the waybars 32. The ends of thewaybars 32 are connected by a plate 33 on which is mounted the clampactuator 34. The clamp actuator 34 consists of a cylinder andreciprocating clamp ram 35. The ram 35 extends slidably through theplate 33 and into a blind bore within the clamping jaw 30 (FIG. 15).

The end of the ram has a head 36 chamferred at37. Where the ram entersthe clamping head 30 it is surrounded by a gland nut 38 which compressesa spring 39 extending between the nut and the head 36. The spring biasesthe clamping jaw 30 toward the collet actuator 34 until further movementin this direction is prevented by bottoming of the head 36 on the blindend of the bore 40. When the head 36 is advanced to the bottom of thebore 40, the chamferred end 37 rides against the cam surface 41 of thetrip plunger 42, forcing the trip plunger 42 outwardly against the biasof the spring 43. The purpose of this will be more fully explainedhereinafter.

Retraction or opening travel of the clamping jaw 30 by the colletactuator 34 is limited by a pair of stops 44 (FIG. 1). Furtherretraction of the ram 35 by the collet actuator 34 withdraws the head 36from the bottom of the bore 40, releasing the trip plunger 42. When thishappens, the trip plunger shifts inwardly to the position illustrated inFIG. 14. The stops 44 are threaded through the posts 11 making themadjustable. This permits the openingof the jawstobe limited only to thatwhich is necessary to receive the work piece. So limiting the size ofthe opening prevents the Work pieces from rocking sideways or fallingthrough the jaws as they are initially dropped between them. The stops44, once properly positioned, are locked by the locking nut 44a. I

Slidably extending through the clamping jaw 30 are a pair of rods on theends .of which are upwardly extending work piece stops 51. Whenthecollet is opened to receive a work piece, the work piece stops arepartially seated within the reliefs 22 and are held against the clampingplate 21 of the backing jaw 20. A portion of the stops extend into theopening to intercept the work piece as it enters the collet. The ends ofthe rods adjacent the collet actuator 34 are joined by a yoke 52.

Between the yoke 52 and the adjacent face of the c1amping jaw 30 acompression spring 53 surrounds each of the rods and urges the rodstoward the collet actuator 34. Thus, the stops 51 are biased to retractinto the reliefs in the lower end of the clamping plate 31 on theclamping jaw 30. Below the ram 35 is a stop 54 designed to engage theyoke 52 just before the backing jaw 20 reaches its maximum retractedposition. The stop 54 presses the yoke 52 against the bias of thesprings 53 toward the clamping jaw 20 shifting the stops '51 into thereliefs 22. Preferably, the stop 54 is resiliently mounted so that itwill permit a limited degree of overtravel thus permitting the rods 50to travel a limited distance with the backing jaw 20' during the lastincrements of movement of the backing jaw.

Mounted on one side of the machine are a pair of hexagonal control bars,one being the upper control bar and the other being the lower controlbar 61. On these two control bars are mounted the sensors which controlthe movements of the machine. On the upper bar are the sensors 62 and63. The sensors 64 and 64 are mounted on the lower control bar 61. Eachof the sensors may be adjusted lengthwise of its supporting control barand when properly positioned for the accurate actuation of the machine,may be secured to the control bar by suitable means such as set screws.

The sensor 62 is positioned to be contacted by the trip plunger 42 whenthe clamping jaw is shifted to collet closed or clamping position. Thesensor 64 is positioned to be actuated by the trip arm 66 on the backingjaw 20 when the backing jaw reaches its maximum retracted position, thatis, its maximum travel to the left as the machine is illustrated inFIGS. 1 and 2. The sensor is designed to be actuated by the trip arm 68when the collet reaches its maximum retracted position. The sensor 63 ispositioned to be actuated by the trip arm 67 on the backing jaw 20immediately after the collet starts its retraction movement.

The manner in which the sensors control the actuation of the machine isset out diagrammatically in FIG. 17. It will be recognized that themachine may be operated either hydraulically or pneumatically. In eithercase, the pressurized fluid is supplied from a suitable source to thetwo selector valves 69 and 70 through the supply lines 71 and 72respectively. The sensors 62, 63, 64 and 65 are poppet or pilot valveswhich when tripped create a pulse which actuates the selector valves.The selector valve 69 has combination supply and exhaust lines leadingto each end of the collet actuator 35. The selector valve 70 hascombination supply and exhaust lines leading to each end of the feedactuator 24. The lines 72 and 73 connect the selector 69 to the colletactuator 35. The selector valve 70 is connected to the feed actuator 24by the lines 74 and 75. Interposed in the line between the sensor 64 andthe selector valve 69 is a suitable time delay mechanism such as an airoperated delay timer which interposes a predetermined delay in thetransmission of the signal from the sensor 64 to the selector valve 69.This delay mechanism is indicated in FIG. 17 by the numeral 76.

The rate of travel of the collet 13 under the influence of the feedactuator 24 is controlled by the velocity control mechanism (FIGS. 2 and16). This mechanism conthe pressure plate 85, one end of which embracesthe piston rod 82 between the stop nuts 83 and 84 and the other end isrigidly secured to the backing jaw 20. The

use of the nuts 83 and 84 permits the distance between them to beadjusted. I I

As best seen in FIG. 16, the piston rod extends into the dual chambers86 and 87 of the dash pot 8 1. -In each chamber, the piston rod isequipped with a piston head, one piston head 88 being in the chamber 86and the other piston head 89 being in 'the chamber =87. The two chambersare separated by a bathe 90 and are connected through the baflie by arestricted bleed passage 91 through which fluid trapped in the chambers86 and 87 can pass only at a predetermined flow rate. The rate at whichthe fluid can pass through the bleed passage 91 may be adjusted by themetering screw 92. The purpose of this will appear more fullyhereinafter. The restricted passage 91 is designed to limit the rate atwhich the fluid may pass from the chamber 86 to the chamber 87 and thusregulate the speed of travel of the collet13 as it shifts to the right,as the machine is illustrated in FIGS. 1 and 2. Movement of fluid fromthe chamber 87 to the chamber 86 is rapid because flow in this directionis through the check valve passage 93. The check valve 94 closes toprevent the use'o'f this passage by fluid attempting to move from thechamber 86 to the chamber 87.

As is best seen in FIG. 6, immediately above the machine is a magazine100 designed to feed work pieces to the machine. Discharge of the workpieces from the magazine 100 is normally prevented by the gate 101 whichis biased by any suitable means such as a spring into work piece holdingposition. MOunted on the collet 13 is a dog 102 which, when the clampingjaw is shifted to open position, engages the gate 101, withdrawing it torelease one of the work pieces. The magazine 100 is shown in greaterdetail in'FIG. 4. It consists of a tube within which the work pieces areloaded and stored ready for release. A

spring 104 is seated with the magazine. The work pieces enter a funnel105 whichaligns them ready one at a time, through'the lower end 106. V

In the following paragraphs the operation of this invention will bedescribed with particular reference to FIGS. 5 through 14.

In FIG. 5, themachineis-shownfat the end of its retraction stroke withthe collet {open ready to'receive a new work piece for machining. Inthis-position, the clamping plates 21 and 31 are separated 'and'theworkpiece stop fingers 51 are partially seated in the reliefs 22 sincethe yoke 52 is pressed against the stop 54 (FIG. 6). The clamping jaw isseated against the stops 44. The ram being fully retracted, the head 36is withdrawn from the bottom of the bore 40 permitting the trip plunger42 to retract.- Also, as is seen in FIG. '6, the gate 101 is withdrawnfrom the'magazine 100, permitting a new work piece A to drop between theclamping plates21 and 31 and seat on the stop fingers 51. Also at thispoint,as is shown in FIG. 5, the trip pin 66is engaged with the sensor'64. This engagement occurs the moment the'collet 13 reaches its maximumadvance position, but the signal generated by the tripping of the sensor64 is delayed by the delay timer 76. Thus, the selector valves actuationis delayed fora dwell period, preferably 'a fraction-ofa second. Duringthis dwell, the work piece A is dropped intothecollet H At the end 'ofthe dwell period, the selector valve 69 actuates the collet actuatorforcing the ram 35 to extend. This shifts the clamping jaw 30 to'a clampposition firmly locking the work piece A in the collet. As the ram 35for discharge,

bottoms in the bore 40, the head 36' forces the trip' plunger 42 toextend, tripping the sensor 62. The pulse from the sensor'62 actuatesthe selector valve- 70-and starts the feed actuator moving to the right,as the machine is'illustrated in FIGS.1 and 2.

As thecollet initiates its movement toward the cutter B, both the tripplunger 42 and the trip pin 6'6 disengage their respective sensors 62and 64. Also, the yoke 52 is moved away from the stop 54 and by reasonofthe bias of the springs 53 (FIG. 1),the rods 50 and their fingers 51'retractinto thesockets 55, leaving the space below the work piece A freeandunobstructed. I

During the movement ofthe clamping jaw to clamping position, the dog 102shifts to the right, as the machine isillustrated, permitting the gate101 to move under the magazine, preventing the discharge of another workpiece.

During the initial increment of movement of the loaded collet toward thetool B, the pressure plate 85 traverses the gap between the stop nuts 83and 84 on the piston rod 82 (FIG. 2'). Thus, the velocity controlmechanism is inactive and the feed actuator'is free to move as fastas'fl'uid is supplied to it. The machine is so designed that the rate oftravel durin this interval is quite rapid. Just before the work piecemakes contact with the tool B; the pressure plate 85 engages the stopnuts 84. Thereafter the collet has to shift the piston82with 'it. Therate at which the collet can shift the piston 82 is governed by the rateat which the fluid trapped in the chamber 86 can be transferred to thechamber 87 through the bleed passage 91. The rate of flow through thispassage has been previously metered by means of the metering valve 92 tothat which will move the work piece past the cutter atthe precise speedrequired by the particular machining operation to be executed. It willbe understood that this will vary, depending on the particular toolbeing used and the particular material being machined."

FIGS. 7 and 8 show the equipment just as the machine initiates itsretraction movement toward the cutter. FIGS. 9 and 10 illustrate theequipment in transit between loading position and the cutting tool B.

FIGS. 11 and 12 illustrate the eqiupment at themoment it reaches thelimit of its retraction stroke, after the work piece A has been carriedpast the cutter and the operation on it has been completed. It will benoted that the trip pin 67 has a pivoted end 77 which constitutes aone-way dog. This permits the trip pin67 to pass the sensor '63 withoutactivating it. The end of the retraction stroke is reached when thesensor 68 trips the sensor 65. At this point, the trip pin 67 has justpassed the sensor 63 a sufficient distance to permit the dog 77 to pivotinto operating position where, upon reversal of movement, the dog willwipe across the sensor 63 tripping it. The tripping of the sensor 65shifts the selector valve 70 reversing the direction of movement of thefeed actuator 24. Immediately the direction of travel of the collet isreversed and the collet starts to advance toward the loading position atthe left hand end of the machine as illustrated.

Immediately upon initiation of the advance move- =ment of the collet,the trip pin 67 trips the sensor' 63. This actuates the selector valve69 causing the collet actuator to retract the ram 35. This opens thecollet to' maximum jaw opening, freeing the completed work piece A todrop through the collet into suitable collection equipment. It will benoted that the pins 51 are retained in retracted position by the springs53 during this period, and thus, do not interfere with the free drop ofthe completed work piece. It is important to note that the machine doesnot pause to unload. Further, it unloadsbefore the work 'piece is movedback past the cutter B,

as is clearly shown'in FIG. 13.

Due to the presence of the check valve passage 93 and the check valvev94, the transfer of fluid from the chamber 87 to the chamber 86 in thevelocity control device, may progress rapidly and thus, the velocitycontrol to the left during the advance stroke, resetting it for the nextoperating cycle. This arangement permits the collet to return to itsload-receiving position rapidly and without interference from the piston82.

As the collet approaches the loading station, the clamping jaw 30engages the stops 44 preventing further return movement. However, sincethe backing jaw will not have reached a position to trip the sensor 64,its re: turn movement will continue until the sensor 64 is tripped. Itscontinued movement partially. closes the opening between the jaws untilit once again is only sufficient to receive the work piece. Just beforecontact is made be tween the clamping jaw 30 and the stops 44, contactwill have occurred between the yoke 52 and the stop 54 extending thestop pins 51 to a position which will partially seat them in thechannels 22 when the backing jaw reaches its maximum return position.This restriction in the size of the jaw opening permits the jaw openingto be set at just that which will receive the part. Thus, parts ofvarious sizes and shapes can be accommodated. For example, it permitsuse of the machine with a headed part which must be delivered to thecollet head down.

It will be seen from the above description that this invention providesa work holder and collet which reciprocates back and fourth past thetool or cutter with a minimum of delay in its operating cycle. At theloading end of the stroke, its dwell period is only that fraction of asecond necessary to receive and clamp a new work piece. This can bereduced to a fraction of a second. At the opposite end of the stroke,the dwell period is only that necessary to reverse the direction ofmovement of the feed actuator 24. No dwell is required for discharge ofthe completed work piece. Thus, the machine operates with maximumefliciency. Further, the machine is so designed that it may be adaptedto the machining of a wide variety of work pieces. It is entirelypossible to use the machine to perform consecutively, several operationsduring the retraction stroke. It is also possible to adjust theoperating speed of the machine during the actual machining operation tofeed rates consistent with a wide variety of materials. While themachine has been illustrated as used with a milling cutter, it will berecognized that numerous other types of machining operations can beperformed on the work pieces utilizing this particular machine. Further,the machine is completely automatic and requires no manual interventionthroughout any portion of its operating cycle. It is readily adjustableto strokes of varying lengths. Therefore, there is no wasted timeinterval while the machine traverses unnecessary distances, not utilizedin the particular operation to which it is applied. The length of thestroke is variable by shifting the sensors 63 and 65 along the stop bars60 and 61. The sensors can be shifted and locked in any locationrequired by the particular operation.

While the machine has been described. as having hydraulic or pneumaticsensors, it will also be recognized that the sensors could be electronicand the selector valves operated by solenoids. Such changes are to beconsidered as within the scope of this invention. It will be recognizedthat other changes can be made in the construction of this inventionwithout departing from the principles of the invention. Suchmodifications are to be considered as within the scope of thehereinafter appended claims, unless these claims by their languageexpressly state otherwise.

I claim:

1. A work holder having a collet with work clamping jaws and meansmounting said collet for reciprocating movement between a first positionand a second position and a regulator element for controlling thereciprocation of said collet; a first actuator for continuouslyreciprocating said collet between said positions; a second actuator foropening and closing the jaws of said collet; said regulator elementactivating said second actuator to close the jaws of said collet whensaid collet reaches said first position; a delay member connected tosaid regulator element for causing said collet to dwell during theclosing of said jaws at said first position; a speed control memberoperatively associated with said collet for varying the speed of travelof said collet during at least one portion of its movement in onedirection, said speed control member being a dual chambered dash pothaving a pair of pistons one in each chamber mounted on a common rod;both of said chambers being fluid filled; an arm connecting said rod tosaid collet and adjustable means on said rod cooperating with said armand forming a lost motion connection between said rod and said arm; arestricted passage connecting said chambers for the passage of fluidwhen said collet and rod are moving in said one direction; a check valveconnecting said chambers and openable to permit the free flow of fluidtherebetween when said collet and rod are moving in the oppositedirection. 7

2. A work holder as described in claim 1 wherein said speed controlmember has an adjustable valve member mounted in said restricted passagefor prcdetermining the speed of travel of said collet during said oneportion of its movement.

3. A work holder having a collet with work clamping jaws and meansmounting said collet for reciprocating movement between a first positionand a second position and a regulator element for controlling thereciprocation of said collet; a first actuator for continuouslyreciprocating said collet between said positions; a second actuator foropening and closing the jaws of said collet; said regulator elementactivating said second actuator to close the jaws of said collet whensaid collet reaches said first position; a delay member connected tosaid regulator element for causing said collet to dwell during theclosing of said jaws at said first position; a workpiece positioningelement in said collet; stop means urging said positioning element intoworkpiece intercepting position when said collet is in said firstposition; resilient means urging said positioning element into retractedposition removed from the opening between said jaws when said jaws areopen and said collet is adjacent said second opening.

4. A fork holder as described in claim 3 wherein said position-ingelement is a pair of fingers and a spring biasing said fingers intoretracted position; said stop means being a resilient stop engaging saidfingers and shifting them against one jaw of said collet as said collectap proaches said one position.

5. A fork holder as described in claim 4 wherein sai one jaw has reliefsin the face thereof to partially receive said fingers; the other jaw ofsaid collet being recessed to receive said fingers when they areretracted by said spring.

6. In a work holder designed to hold and move a work piece past the toolof a machine, said work holder having a pair of jaws forming a workclamping collet and a supporting way on and along which said collet mayslidably travel between work piece receiving and work piece releasingpositions; first actuator means mounted to said collet for traveltherewith and for opening and closing said jaws of said collet; secondactuator means for moving said collet lengthwise of said ways, theimprovement in said work holder comprising: a first sensor tripped bysaid first actuator when the jaws of said collet reach closed positionat said work piece receiving position; said first sensor beingoperatively connected to said second actuator for initiating retractiontravel of said collet past the tool; a second sensor actuated by saidcollet at the limit of its travel toward work piece releasing position,operatively connected to said second actuator for reversing itsdirection of travel; a third sensor actuated by said collet uponinitiation of its advance travel toward work piece receivingposition'and operatively connected to said first actuator for reversingits travel and opening said jaws for releasing the work piece as saidcollet returns to its work piece receiving position; a speed controlelement operatively connected to said collet for sensing the positionthereof along said way and for varying the rate of travel of said colletin response to its position on said way; a work piece positioning membermounted on one of said jaws; a spring biasing said positioning memberinto retracted position toward said one jaw and removed from the openingbetween said jaws; means at said work piece receiving position engagingsaid positioning member and urging it into advanced work pieceintercepting position between said jaws.

7. A work piece holder as described in claim 6 wherein said one jaw isrecessed to receive said positioning mem her when it is retracted.

8. A work piece holder as described in claim 7 wherein all of saidsensors are mounted for adjustment lengthwise of said way for increasingor decreasing the distance traveled by said collet.

9. A work holder having a collet with work clamping jaws and meansmounting said collet for reciprocating movement between a work piecereceiving first position and a second position; a first actuator forcontinuously reciprocating said collet between said positions; a secondactuator for opening and closing the jaws of said collet; said secondactuator opening said jaws of said collet during the collets returnmovement from its second to its first position; a stop member engagingone of the jaws of said collet as said collet approaches said firstposition, said stop member restraining further movement of said one jawto effect a partial closing of said jaws by cont-inued movement of theother of said jaws.

10. A work holder as described in claim 9 wherein a work piecepositioning element is provided in said collet; stop means urging saidpositioning element into work piece intercepting position when saidcollet is in said first position; resilient means urging saidpositioning element into retracted position removed from the openingbetween said jaws when said jaws are removed from said first position.

11. A work holder as described in claim 10 where-in said stop means isresiliently mounted and resiliently urging said work positioning elementagainst the other of said jaws, said stop means permitting said workpositioning element to travel with said other jaw against the bias ofthe stop means resilient mounting.

12. A work holder having a collet with work clamping jaws and meansmounting said collet for reciprocating movement between a work piecereceiving first position and a second position and a regulator elementfor controlling the reciprocation of said collet; a first actuator forcontinuously reciprocating said collet between said positions; a secondactuator for opening and closing the jaws of said collet; said regulatorelement activating said second actuator to open said jaws of said colletafter said collet has reached said second position and has initiated itsreturn movement toward said first position to discharge a work pieceduring its return movement.

13. A work holder having a supporting way and a collet mounted thereonfor reciprocation therealong, a first actuator for reciprocating saidcollet along said way from a work piece receiving position to a workpiece completed position remote therefrom and returning said collet tosaid work piece receiving position, said collet having a pair of workpiece receiving jaws and a second actuator for opening and closing saidjaws, the improvement in said work holder comprising: said secondactuator closing said jaws when a new work piece has been receivedtherebetween; a delay member connected to said first actuator forcausing said collet to dwell during the closing of said jaws at saidwork piece receiving position; a member sensitive to and actuated by theresistance pressure exerted by said jaws when fully closed upon a workpiece deactivating said delay member to initiate travel of said collettoward said work piece completed position.

14. A work holder having a collet with work clamping jaws and meansmounting said collet for reciprocating movement between a first positionand second position and a regulator element for controlling thereciprocation of said collet; a first actuator for continuouslyreciprocating said collet between said positions; a second actuator foropening and closing the jaws of said collet; said regu lator elementactivating said second actuator to close the jaws of said collet whensaid collet reaches said first position; a dash pot having a piston anda cylinder, one of said piston and cylinder being secured against linealmovement and the other having a lost motion connection to said colletfor varying the speed of travel of said collet during at least a portionof the collets movement from said first to said second positions.

References Cited UNITED STATES PATENTS 1,355,167 10/ 1920 Rich 9-0-211,976,105 10/1934 Archea -21.5 2,542,986 2/1951 Bowen 9021.02 2,577,76612/1951 Johnson et a1 90-21.02 2,582,012 1/ 1952 Currier 90-2102 FRANCISS. HUSAR, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,391,606 July 9, 1968 Sylvan J. Kaminga It is certified that errorappears in the above identified patent and that said Letters Patent arehereby corrected as shown below:

Column 1, line 15, "upon initiation of return movement to work piececlamping of the work piece" should read and initiating advance movementupon proper clamping of the work piece Column 2, line 1, "moves the workpiece" should read devices which are automatically removed as themachine moves the work piece Column 4, line 35, "The sensors 64 and 64"should read The sensors 64 and 65 Column 8, line 42, "A fork holder"should read A work holder line 48, "A fork holder" should read A workholder Signed and sealed this 13th day of January 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissionerof Patents WILLIAM E. SCHUYLER, JR,

